Mill plate



March I2, 1929. o. SHEPPARD, JR J 1,705,379

MILL PLATE Filed Feb. 1, 1924 s Sheets-Sheet 1 March 12, 1929. o.SHEPPARD, JR

MILL PLATE Filed Feb. 1, 1924 5 Sheets-Sheet 2 a vwemtoz Orlando fhpparqJ" flfl'ornu;

o. SHEPPARD, JR

MILL PLA'IE' Filed Feb. 1, 192

5 Sheets-Sheet 3 wue-ntoz Patented Mar, 12, ll929.

entree rattan ORLANDO snnrrnan, Ja, OFATLANTA; GEORGIA.

MILL PLATE.

Application filed February The present invention provides improvementsin grinding mills, these improve ments being applicable generally tomills of the kinds employing opposed relatively revoluble grindingplates between the faces of which the material is ground or reduced.

A primary object of the invention is to provide novel and improvedgrinding plates for attrition mills of the type employing plates havingribs and pockets in their faces between which the material is ground orreduced. l-leretofore it has been proposed to provide the faces of theplates with ribs, some of which extended radially of the axis of theplate and other ribs which extended in a direction generallycircumferentially oi the plates, pockets being formed between the ribs,but in the ribbed constructions previously proposed, the circumferentialribs of the opposed plates either produced no grinding action betweenthem or such grinding action as may have been produced between thecircumferential ribs occurred only through portions of the relativerotationof the plates, and'hence the capacity of the mill was limitedeither wholly or largely to the grinding action which occurred betweenthe radial ribs, and furthermore, in such previously proposedconstructions, the radial ribs became worn rapidly and also unevenly,thus prematurely rendering the plates unfit for further use. The presentinvention provides grinding plates for mills of this type wherein theribs which extend in a direction generally circumferentially of theplates so arranged that they cooperate at all times during the operationor throughout the relative rotation of the plates to produce betweenthem a shearing or grinding action upon the interposed material incourse of reduction, these ribs thus co-acting with the radial ribs toafl'ord the maximum grinding efficiency and capacity for a mill. ofgiven size, and, furthermore, the wear will be distributed uniformly between the radial and circumferential ribs, so that the period ofusefulness of the plates greatly extended. Moreover, the presentinvention provides aribconstruction which presents two sets of grindingedges, one of -which sets can be brought into use after the other sethas become worn or their efliciency has become impaired, it providesplates which may be made in sections which are identical, and hence ofequal weight, so that the assembled plates will be inherently 1, 1924-.Serial No. 690,005.

balanced, thus obviating the necessity of providing balance-weights orother balancing means for the plates, and it also provides otherimprovements in the grinding plates which increase the efiiciency of themill and obviate objections found to exist in attrition mill plates asheretofore proposed.

Another object of the invention is to pro- I vide a reinforced structurefor the grinding plates or members oil attrition mills, disk hullers andsnmlar mills where the grinding plates or members revolve at relativelyhigh speeds. Heretofore, it has been usual to make the grinding platesof relatively soft steel or other cast metal, in order to reduce theliability of the plates to fly apart under centrifugal force and therebydamage or wreck the mill,v when the plates become cracked or broken, dueto the entrance of a piece of metal or other foreign substance be tweenthe plates, or to other causes, but in constructing the plates ofrelatively soft ferred' to, the durability of the plates is accordinglyreduced. The present invention provides areinforced structure for suchplates whereby the plates may be made of relatively hard cast steel ormetal which will afford greatly increased durability and wearingproperties for the plates, and the reinforcement will preventfiyingiapart of the plates, should they become cracked or broken, and,moreover, the reinforcement will retain the broken parts of the platesin proper position so that the-use of the plates can be safely continueduntil they have served their usual period of usefulness.

To these and other ends, the invention J consists in certainimprovements and combinations and arrangements of parts, all as will behereinafter more fully described, the features of novelty being pointedout particularly in the claims at the end of the specimetal in ordertominimize the damage rean enlarged scale,

a section taken radially through a pair of attrition mill plates andtheir supporting disks constructed as shown in Figures 1 and Figure irepresents, on an enlarged scale, a section taken radially through oneof the plates constructed as illustrated in Figures 1 to 3, inclusive;

Figure 5 is a detail view of a reinforcement provided by the presentinvention and applicable to attrition plates and also to the plates ofdisk hullers other mills, the dot-and-dash line outlining a portion ofthe mill plate in which the reinforcement is adapted to be embeddedFigure 6 represents a section on the 6-6 of Figure 5 illustrating themanner which the reinforcement is embedded in the mill plate; and

Figure 7 is a'diagrammatic view illustrating the preferred mode ofgenerating or laying out the substantially circumferential ribs of theimproved plates.

Similar parts are designated by the same reference characters in theseveral views.

The preferred embodiment of the invention is shown in the accompanyingdrawings and will be hereinafter described in detail. It is to beunderstood, however, that the invention is not restricted to theparticular construction shown, as equivalent constructions arecontemplated and such will be ineluded within the scope of the claims.

In the present instance, 1 designates the disks such as thoseconmionlyused in attrition mills, these disks being mounted respectivelyon shafts 2 which may be driven in relatively reverse directions in theusual way,

[the material to be ground or reduced being fed in the usual way betweenthe disks and the material feeding outwardly or toward the periphedcs ofthe disks under centrifugal force, the material while passing outwardlybeing ground or reduced between the opposed faces vofthe plates 3, thelatter being preferably fitted into recesses 4 formed in the outermarginal portions of the disks and secured therein by a suitable numberand arrangement of bolts 5. The plates 8 in the grinding ribs posedplates, throughout the relative rotation of the plates, in consequenceof which maximum grinding efficiency and capacity are obtained, the weartakin place is dis tributed uniformly between the circumferential andradial ribs, and other advantages are secured over attrition mill platesas previously proposed. Preferably and as shown in the present instance,the working face of each plate section 3f is formed with an outerperipheral rib 6 which is concentric with the axis of the plate or thedisk on which it is mounted, and the working face of each. plate sectionis provided with a suitable number of ribs 7' which extend in adirection generally circumferentially of the plate but with a pitchtoward the outer edge of the plate, and with intervening or connectingribs 8, which latter extend radially of the plate, pockets ordepressions 9 being formed between the radial ribs and the ribs 7 andbetween the radial ribs and the outer rib 7 and peripheral concentricrib 6. The ribs 7, according to the present invention are so located andarranged on eachplate section that the plate made up of these sect-ionswill present these ribs 7 to corresponding ribs on the opposed plate insuch a manner that rotation of the opposed plates in reverse directionswill produce continuous or uninterrupted shearing'or tion join with orform continuations of the corresponding ribs of the adjacent platesections. To obtain these results, the ribs 7 preferably extend on arcsof circles, the centers of which are offset relatively to the center ofrevolution of the plate. Figure 7 illustrates diagramn'iatically onemode of generating the circumferential ribs 7. In this diagram 0 is thecenter of the inner and outer circles a and 5, while 0 and 0 are centersabout which are described the lines 7" and '7" respectively, which liebelow and above the line or diameter AB. "By appropriately locating thecenters 0 and 0 the arcs 7 which lie below the line'AB will join thearcs 7" which lie above the line AB. Two diagrams conforming with thatshown in Figure 7, if reversed and superposed, would present the lines 7and 7 of the opposed diagrams in such manner that they will not coincideat any point in their circumferences or at any point when relativelyrotated, but such lines will always intersect one another at a number ofpoints around the circumferences of the diagrams as the latter arerelatively rotated, and if grinding plates were made havingcircumferential ribs arranged thereonin accordance with the lines 7 and7" of this dia ram continuousv grinding action would be produced betweensuch circumferential ribs. However, it is desirable in practice toconstruct each grinding plate of a number of sections and it is alsodesirable that all sections of the grinding plate be of identicalconstruction in order not only to facilitate manufacture and maintenanceby the use of a single pattern and interchangeable plate sections, butalso to obtain inherent balance in the plate. It will be found that ifthe diagram is intersected by the lines or dia'-' meters wrc and 1 sothat these lines, to gether with the line AB divide the diagram into sixsegments of equal circumferential length, the lines 7 and 7" of one diagram, when superposed upon a duplicate diagram, will intersect on thelines-Al3, m.r and y aI and hence any one of the duplicate segments ofthe diagram lyingbe tween the lines AB and QJ-% and pattern for a set ofplate sections, and a plate made up of such sections would embodycircumferential ribs which would produce continuous shearing actionthroughout the revolution of the opposed plates, and, moreover, thecircumferential ribs of any section of the plate would be continuouswith the corresponding circumferential ribs of adjacent sections.Preferably and as shown in the present instance, one of the duplicatesegments of the diagram lying between the line mw and AB issubstantially adopted as a pattern for the circumferential ribs 7 of theplate section, each of these segments constituting one-sixth of thecircumference of the diagram and accordingly the'plate is constructed ofsix sections which will be of identical circumferential rib formation.

In the particular construction shown, 0 is the approximate center of thecircumferential ribs of each of the respective plate sections as theseribs are shown in 2, it being understood that the centers of thecircumferential ribs of each plate section are nearly or substantiallycoincident, and

that the centers of the ribs of the different plate sections are locatedin eccentric relation to, and are spaced eccentrically around, thecenter 0 about which the plate revolves. ,Each of these circumferentialribs is preferably an arc of a true circle with its center ,so locatedthat each of such ribs extends from a point within the periphery of theplate section outwardly toward the periphery thereof and so that eachcontinuous circumferential rib of the plate extends-from the inner edgeof the working face of the plate continuously through the differentsections to the peripheral portion of the plate, the ends of thecircumferential ribs of any one section alining with or formingcontinuations of the corresponding ribs of the adjacent plate sections.Of course,

there will be six sets of these rib centers located around the center 0,in the construction herein shown, to conform with the use-of sixcircumferentially extending but outwardly-pitched ribs. It willbe'understood, however, that any equivalent arrangement of thecircumferential ribs which will produce continuous grinding action uponthe inaterial between the plates throughout their revolution maybe used,although 7 it is'also desirable that the circumferential ribs of oneplate section should be continucircumferential rib are substantiallyperpendicular to the'plane of the working face It will also of the plateto provide efficient cutting edges on the inner and outer sides of eachof these ribs, so that when one edge of the circumferential ribs of eachplate has become worn, the mill disks carrying the plates may bereversed and the operation of the mill then be continued,bringing'theouter edges of the circumferential ribs of the opposedplates into operation. In this way, greatly increased serviceability ofthe grinding plates is obtained. In order to facilitate the passage ofthe material undergoing reduction between the working faces of theplates and also to avoid banking or packing of the material against theinner walls of the circumferential ribs and thereby disturbing thebalance of the plates, a fillet 7 is preferably formed at the innersideof each circumferential rib between its face and the body of theplate, but this fillet terminates short ofthe workingfa'ce of ther1b,-thus leaving an effieient cutting edge at the inner side of therib, similar to the cutting edge at the outer side of such rib. Thesides of the radial ribs 8, as shown, are preferably substantiallyperpendicular tothe plane of the working face of the plate,

so that these ribs present efiicient cutting edges at both sidesthereof. Thecircumferential ribs 7 and the radial ribs 8 preferablyreduction, but the working faces of the ribs. from the inner edges ofthe plates outwardly to the line LL are preferably beveled slightly sothat they converge as they approach the line L.L, this bevel of theworking faces of the ribs facilitating the feeding of the materialbetween the plates and thus promoting the grinding action. The inneredge of each plate is also preferably formed with a beveled feedingsurface 10 and a suitable number of breaker ribs 11 are preferablyprovided which project forward from the feeding surface 10, thesebreaker ribs serving to break up the material which may be fed to theplates in the form of cakes or lumps, thereby facilitating the entranceof the material between the working faces of the plates. I

In using a pair of plates each constructed substantially as hereinbeforedescribed, the plates, when placed opposite to one another will presentthe ribs 7 to one another in such relation that they will alwaysintersect at a number of points throughout the relative rotation of theplates, the ribs 7 avoiding coincident superposition at any point, and

'in the operation of this mill, during which the plates are relatively,rotated, it being usual to revolve both plates but in oppositedirections, the ribs 7 ofthe opposed plates will produce and maintain acontinuous shearing action between them and also between these ribs 7 ofeach plate and the radial ribs 8 of the opposed plates, Figure 2 showingclearly the shearing relation be-' tween the ribs 7 of the opposedplates. In consequence, maximum grinding efliciency and capacity areattained and the wear of the plates is distributed uniformly between thecircular or circumferential ribs 7 and the radial ribs 8 so that theworking faces of the plates are maintained in efficient workingcondition for a maXimum period of time.

The present invention also provides means for reinforcing attrition millplates and also the plates of disk hullers or other mills which aresubjected to centrifugal and other strains while in operation and which,if broken in consequence of the entrance of a foreign body between theplates, or from other causes, would fly apart and damage or Wreck themill or the entire set of plate sections in the mill. Heretofore, thestrength and durability of grinding plates have depended upon the kindor quality of raw material from which they were made and the v theirperiod of usefulness, and if hard enough to sustain wear for a longerperiod would be brittle, and hence subject to breakage and destruction.Difficulties in obtaining castings of uniform quality of hardness haveresulted in the production of mill plates, some of which were too softto sustain wear for a sutlicient period of time and others were too hardand hence were subject to breakage and destruction.

The present invention provides a reinforcement adapted to be embodied ina mill plate or the sections thereof and capable of greatlystrengthening the same so that it will greatly resist breakage and ifbreakage of the plate or plate section should occur, the reinforcementwill serve to retain the fragments or broken parts of the plate or platesection in proper position, thus not only avoiding damage to ordestruction of the mill, but also enabling the operation of the mill tocon inue until the plates have served their usual period of usefulness.

In the present instance, a reinforcement is f shown which suitable foruse in attrition mill and disk huller plates, the reinforcementcomprising a mesh composed of a suitable number and arrangement of bars12 and 13 of tough steel or other suitable material capable ofwithstanding breakage, either or both of these rods at theirintersections being preferably offset, as at 14, to produce a fasteningor interlocking engagement be tween them. This mesh is embedded in themill plate or mill plate section by casting the steel or metal composingthe plate around the reinforcement, so that the reinforcement lies in aplane about midway of the thickness of the plate and in the plane ofrotation thereof. Preferably and shown in the present instance, the rod18 in. the middle of the plate section extends radially thereto and theother rods 13 are suitably spaced in parallelism with the middle rod,these rods adjacent to the plate-securing bolts 5 being preferablyspaced more closely than at other parts of the plate section in ordertosecure greater reinforcement of the plate section in the regions ofthe securing bolts. The reinforcement bars 12, as shown in the presentinstance, intersect the bars 18 at or substantially at right angles andthey are suitably spaced between the inner and outer edges of the )latesection.

In using a rein orcement substantially as herein shown and described,the grinding plate may be composed of a steel or material much harderthan it has heretofore been possible to use with safety, so that thegrind greatly strengthens the plate so that'itis" capable or P88153111,'to a high degree, forces weak it, and tthe plate ing plate will possessear-resisting proper-i ties to a high degr e, and hence the useful 'nessof the plate ivill be-greatly prolonged.

The. reinforcern ht which isen'veloped by the steel or rnaterlalcomposing the grind ng plate and 11s nitiu'nately unlted therewith,

tendin .orrackor should become broken, the reinforcement will hold thefragments or parts of the plate or plate section in proper position,thereby Y not only avoiding damage to the mill, but 1 alsoenabhng theoperation of the null to {section until the plate, a period oiusciulness,

continue, using" the brokenplate oi plate has jserved its usual I Thepreferred to in of ribs on the workjng faces of the plates has beenheretofore) described whereby continuous shearing ac-7 r ionon the.niaterial undergoing reduction will. be produced, throughout therelative revolution ofthe plates, between'the genlly circumierentiallyeitending' u ward, 1y" pitched .ribsof' the opposed plates, and

between the generally circuniferentially eX- grinding efiicienoy and"increased capacity for' a hull of given sizeybut itsisto be; un-

derstood thatother or equivalent rib formations inay be used toobtainsubstantially the It is preferable, however, to

smile results; v form the generally'circurnferentially extending ribs as"arcs of true circles having .a pitch from the inner toward the. outeredge o ftlie plates, substantially as herein shown,

and to'construct each plate of a pli'irality of' identical segmentalsections so that the ends of, the circuin ferentially extending ribs-ofany section aline or are continuousvvith the I er ivear' resisting'.properties than' it.-h'as been; heretofore? safe "to use, for.notw'itlr standing the liability fof b'r'je'akageuofsuchcircumferentialcribs' of adjacent sections,

I {the manufacture of theplates'beingthusfa c'ilitated, the plates beinginherently loal ancedfandundue ear 0 grooving of'the radial ribs beingavoided; It-is' al so pref- 'l e o for the ircum erent y en ingeutivardly pitched ribs with right "an led or efficiently-shaped innerand outer cuttiiigeclges whereby the period ofus'eful nessof'the platesmay be increased by reversing the mill disks carrying the plates,

after one pair of the cutting edges provided by these ribs has becomeWorn, thus br nging ,7 the other set of cutting edges into; operation.:The fillets at the inner sides ofthel circiunferenti allyextending ribsare preferably used as theyfacilitate the outward- 1 feed of the'niateri'al undergoing reduction and they also avoid banking of thematerial" againsttheiinner sides ofthese ribs and which, it allowed tooccur, lvv ould unbalance fl llflp l l Y I Preferab ly, and as shown inthe present instance, one o'f' the-circumferential ribs commences on"each of the plate sections,- these ribs extendlng around the face ofthe' plate so that the portions of these ribsborne each plate sectionare ali'nedf. this dentical circumferential rib formation all of thesections and the sections Will be entially by'portions of; other ribs;"Inthe particular construction shoivnyflthe circun1- ieren'tial ribs arealso located; symmetrically on-the' working face of the plate,tll1ecenters of these ribs being 7' located, eccen trically of and spacedsymmetrically around the axis of rotation of the plate,f and hencehcrentlybalanced, the number ofjcircuin .ierential ribscorrespondingkvfih the nuni-f ber of plate sections used, and eachcircum-- :lferentialrib will be overlapped circumfen "angeniont, eachplate section ill have an I ,"thereon, so that one pattern will servefor thcdifferent circumferential ribs'vvillstalrt at points s ginnerport 1 of thei Workingfface otjgthe plate "and \v1ll tern"11 nate'at polnts spaced such f ribsn I I I ng functron here n descr bed, buttheymay also cedsymmetrically around the 7 V p 00 *syinn et ically*around 'fthe outer portion of V c. g course, the circurnferentlal Y conly perforintheshearing or grind ter-ial priorto itsfinal'dis'chargeattheperiphery of th'e plates. V i r 1 i The reinforcement provided by,the" present invention enables thef' grindingfplates I of. mills"oi'fflvarlous tfy'z p'es or l'rinds to; be

constructed or hardenmaterialfand of great plates, due to the increased;'hardness flof -theanaterial=coinposjinglthem,the reinforce-j 3, .nientnot only resists; forces tending to break plates,- but j shouldse'ctiongf oii'ieither r xpiate be'coniej' broken, its parts will beheldtogether and in proper working position, so

thattheoperation of? the mill'inay be safely continued,- the brokenplate section operating substantially as if unbroken. The preferred formof the reinforcement as applied to attrition' inill platesis hereinshown and-def; I scribed, but it is to beunderstoodthat the I Vreinforcement may take other forms in plying it tothe grinding plates ofattrition inills," disk hullers or to the grinding plates of mills ofother types; Obviously, if'the j. mill plate, to which}thereinforcernent is] ap'plied is const-ructjed v in"one pie'ceinsteadlof in segments, the forlrn oi? tl 1 e rein; 1130s iforcement maybevari'ed to I conform there 'with.

I, claim as my'invention A grinding plate for mills having a fw'orking'face provided with a set of pro-- je'cting' ribs which extendcircumferentially [of the plate, the inner side 'ofeach rib hav- Ling aportion. extending substantially per- ,pendicularly to and forming acutting edge with the face or the rib, and a fillet oining thel face ofthe plate with said portion of the inner side of the rib at a pointremoved I n from, saidc'uttin'g edge. I

} QXA reversible grinding plate for millshaving a working face providedwith a set 7 of projecting ribs, which extend circumferentially and arepitched outwardly from vpoints toward the inner side to points to- Iward the outer perlphery of the plate, the

inner side of each rib having portion extending atl an angle to the faceof the plate to form, a cutting edge with the face of the ,rib, and atilletjoining theface of the plate .removed from said cutting tainingfragments, broken from the plate,

in' working position.

Q 4. A grinding plate for mills comprising a body of hard caststeel'havingva dressed working face and a tough steel rod:r'einforcement embedded in the body behind said i dressed face andintimately united there-* witlrand operative to maintain fragments,

c T broken fro1n- ,the p late,- in working position.

A;- gr'1nding;plate;;comprising a body-M r I I stresses towhlch theplate is sub' ected. while in "operat on to maintain fragments I of 'acomposed fofhard cast steel having a dressed working face and a strainsustaining -rein forcement 1 composed of tough steel embed d'edinthe'body in aflplanebehind its work- --{ing face; saidreinforcementbeing intimate- I 1y united with the hard cast steelcomposing a the body. and operative to maintain frag- -op eration.

ments, broken from the platefin'working position.

6. A grinding plate comprising body of hard cast steel having a dressed"working face and an intersecting rod reinforcement composed of tough"steel-embedded insaid bodyand intimately united'therewith, saidreinforcement constituting a strain-sustaining structure capable ofmaintainingfragments of a broken plate'in working position. 1"

7. A grinding plate comprising a body of hard cast steel having adressed working face and a tough: steel reinforcement embedmentembodying. sets'of intersecting menibers, the members of one set-beingrecessed to-engage andinterlock with thef members of the'othcr set,thereinforcement being opded in the bodybehind saidd'ressed face andllllilll'lttelyilnll ttl illlQIGWlill,StLl(l TGHIfOICtF g its faceand'coinposed, ofa hardsteel cast-c ing which alone is too brittle topreclude fracture under the stresses tdwhich such plates; are sub ected'n service, and a reinfor'cement about which said body is cast andintimately united therewith, said reinforceni'entfbeing' operative tomaintain fragments,

during operation. V v p 9. An attrit1on-m1ll 'plate comprising a brokenfrom the plate,in working position "body composedof a hard steel castingof in sufficientresistance alone to preclude frac-- t'ure underthe.stresses to which such plates are sub ected in service andhavinga'r-ibbed working face, and a tough steel reinforce ment .about'whichsaid body is cast and with which it is intimately united, saidreiiiforcement lying} infa pla11e- 'behind said ribbed working face, and belng.operative to-sustain fracturedplate inworkingrelation during or g 95, 7In testimony whereof I have hereunto set i r OBLANDOSHEP-PABD, JR, 5;

